Abstract: Based on the measurement principle of the Faraday rotation angle of the automatic identification system (AIS) of spaceborne ships in this paper, a new method is proposed for calculating the global ionospheric total electron content (TEC). Through the AIS receiver and polarized antenna mounted on the “Tiantuo-5” satellite, the Faraday rotation angle is calculated using the power information received by the polarized antenna, and the TEC value is inverted through the conversion relationship between the TEC and the Faraday rotation angle, and the regional TEC map is constructed based on the TEC values estimated by the Kriging method. The results show that the maximum error ratio between the TEC value measured by this method and the TEC value detected by IGS is about 10%, and the general range of error is between 0.3−0.8 TECU, and the maximum difference between the estimated value and the TEC value of IGS is 1.5 TECU. The estimated result is in good agreement with the TEC value detected by IGS, which verifies the feasibility of this method.